1mInter-Client Exchange Library0m 1mVersion 1.00m 1mX Consortium Standard0m 1mX Version 11, Release 6.40m 4mRalph24m 4mMor0m X Consortium Copyright © 1993, 1994, 1996 X Consortium Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documenta- tion files (the ``Software''), to deal in the Software with- out restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the fol- lowing conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED ``AS IS'', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PUR- POSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE X CONSOR- TIUM BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. Except as contained in this notice, the name of the X Con- sortium shall not be used in advertising or otherwise to promote the sale, use or other dealings in this Software without prior written authorization from the X Consortium. X Window System is a trademark of X Consortium, Inc. 1m1. Overview of ICE0m There are numerous possible inter-client protocols, with many similarities and common needs - authentication, version negotiation, byte order negotiation, and so on. The Inter- Client Exchange (ICE) protocol is intended to provide a framework for building such protocols, allowing them to make use of common negotiation mechanisms and to be multiplexed over a single transport connection. 1m2. The ICE Library - C Language Interface to ICE0m A client that wishes to utilize ICE must first register the protocols it understands with the ICE library. Each proto- col is dynamically assigned a major opcode ranging from 1-255 (two clients can use different major opcodes for the same protocol). The next step for the client is either to open a connection with another client or to wait for connec- tions made by other clients. Authentication may be required. A client can both initiate connections with other clients and be waiting for clients to connect to itself (a nested session manager is an example). Once an ICE connec- tion is established between the two clients, one of the clients needs to initiate a 4mProtocolSetup24m in order to "acti- vate" a given protocol. Once the other client accepts the 4mProtocolSetup24m (once again, authentication may be required), the two clients are ready to start passing messages specific to that protocol to each other. Multiple protocols may be active on a single ICE connection. Clients are responsible for notifying the ICE library when a protocol is no longer active on an ICE connection, although ICE does not define how each subprotocol triggers a protocol shutdown. The ICE library utilizes callbacks to process incoming mes- sages. Using callbacks allows 4mProtocolSetup24m messages and authentication to happen behind the scenes. An additional benefit is that messages never need to be buffered up by the library when the client blocks waiting for a particular mes- sage. 1m3. Intended Audience0m This document is intended primarily for implementors of pro- tocol libraries layered on top of ICE. Typically, applica- tions that wish to utilize ICE will make calls into individ- ual protocol libraries rather than directly make calls into the ICE library. However, some applications will have to make some initial calls into the ICE library in order to accept ICE connections (for example, a session manager accepting connections from clients). But in general, proto- col libraries should be designed to hide the inner details of ICE from applications. - 1 - 1mInter-Client Exchange Library X11, Release 6.40m 1m4. Header Files and Library Name0m The header file <4mX11/ICE/ICElib.h24m> defines all of the ICElib data structures and function prototypes. 4mICElib.h24m includes the header file <4mX11/ICE/ICE.h24m>, which defines all of the ICElib constants. Protocol libraries that need to read and write messages should include the header file <4mX11/ICE/ICEmsg.h24m>. Applications should link against ICElib using -lICE. 1m5. Note on Prefixes0m The following name prefixes are used in the library to dis- tinguish between a client that initiates a 4mProtocolSetup24m and a client that responds with a 4mProtocolReply24m: · 4mIcePo24m - Ice Protocol Originator · 4mIcePa24m - Ice Protocol Acceptor 1m6. Protocol Registration0m In order for two clients to exchange messages for a given protocol, each side must register the protocol with the ICE library. The purpose of registration is for each side to obtain a major opcode for the protocol and to provide call- backs for processing messages and handling authentication. There are two separate registration functions: · One to handle the side that does a 4mProtocolSetup0m · One to handle the side that responds with a 4mProtocolRe-0m 4mply0m It is recommended that protocol registration occur before the two clients establish an ICE connection. If protocol registration occurs after an ICE connection is created, there can be a brief interval of time in which a 4mProto-0m 4mcolSetup24m is received, but the protocol is not registered. If it is not possible to register a protocol before the cre- ation of an ICE connection, proper precautions should be taken to avoid the above race condition. The 4mIceRegisterForProtocolSetup24m function should be called for the client that initiates a 4mProtocolSetup24m. __ | - 2 - 1mInter-Client Exchange Library X11, Release 6.40m int IceRegisterForProtocolSetup(4mprotocol_name24m, 4mvendor24m, 4mrelease24m, 4mversion_count24m, 4mversion_recs24m, 4mauth_count24m, 4mauth_names24m, 4mauth_procs24m, 4mio_error_proc24m) char *4mprotocol_name24m; char *4mvendor24m; char *4mrelease24m; int 4mversion_count24m; IcePoVersionRec *4mversion_recs24m; int 4mauth_count24m; char **4mauth_names24m; IcePoAuthProc *4mauth_procs24m; IceIOErrorProc 4mio_error_proc24m; 4mprotocol_name0m A string specifying the name of the protocol to register. 4mvendor24m A vendor string with semantics specified by the protocol. 4mrelease24m A release string with semantics specified by the protocol. 4mversion_count0m The number of different versions of the protocol supported. 4mversion_recs0m List of versions and associated callbacks. 4mauth_count0m The number of authentication methods supported. 4mauth_names0m The list of authentication methods supported. 4mauth_procs0m The list of authentication callbacks, one for each authentication method. 4mio_error_proc0m IO error handler, or NULL. |__ 4mIceRegisterForProtocolSetup24m returns the major opcode reserved or -1 if an error occurred. In order to actually activate the protocol, the 4mIceProtocolSetup24m function needs to be called with this major opcode. Once the protocol is activated, all messages for the protocol should be sent using this major opcode. A protocol library may support multiple versions of the same protocol. The version_recs argument specifies a list of supported versions of the protocol, which are prioritized in - 3 - 1mInter-Client Exchange Library X11, Release 6.40m decreasing order of preference. Each version record con- sists of a major and minor version of the protocol as well as a callback to be used for processing incoming messages. __ | typedef struct { int major_version; int minor_version; IcePoProcessMsgProc process_msg_proc; } IcePoVersionRec; |__ The 4mIcePoProcessMsgProc24m callback is responsible for process- ing the set of messages that can be received by the client that initiated the 4mProtocolSetup24m. For further information, see section 6.1, ``Callbacks for Processing Messages.'' Authentication may be required before the protocol can become active. The protocol library must register the authentication methods that it supports with the ICE library. The auth_names and auth_procs arguments are a list of authentication names and callbacks that are prioritized in decreasing order of preference. For information on the 4mIcePoAuthProc24m callback, see section 6.2, ``Authentication Methods.'' The 4mIceIOErrorProc24m callback is invoked if the ICE connection unexpectedly breaks. You should pass NULL for io_error_proc if not interested in being notified. For further informa- tion, see section 13, ``Error Handling.'' The 4mIceRegisterForProtocolReply24m function should be called for the client that responds to a 4mProtocolSetup24m with a 4mPro-0m 4mtocolReply24m. __ | - 4 - 1mInter-Client Exchange Library X11, Release 6.40m int IceRegisterForProtocolReply(4mprotocol_name24m, 4mvendor24m, 4mrelease24m, 4mversion_count24m, 4mversion_recs24m, 4mauth_count24m, 4mauth_names24m, 4mauth_procs24m, 4mhost_based_auth_proc24m, 4mprotocol_setup_proc24m, 4mprotocol_activate_proc24m, 4mio_error_proc24m) char *4mprotocol_name24m; char *4mvendor24m; char *4mrelease24m; int 4mversion_count24m; IcePaVersionRec *4mversion_recs24m; int 4mauth_count24m; char **4mauth_names24m; IcePaAuthProc *4mauth_procs24m; IceHostBasedAuthProc 4mhost_based_auth_proc24m; IceProtocolSetupProc 4mprotocol_setup_proc24m; IceProtocolActivateProc 4mprotocol_activate_proc24m; IceIOErrorProc 4mio_error_proc24m; 4mprotocol_name0m A string specifying the name of the protocol to register. 4mvendor24m A vendor string with semantics specified by the protocol. 4mrelease24m A release string with semantics specified by the protocol. 4mversion_count0m The number of different versions of the protocol supported. 4mversion_recs0m List of versions and associated callbacks. 4mauth_count0m The number of authentication methods supported. 4mauth_names0m The list of authentication methods supported. 4mauth_procs0m The list of authentication callbacks, one for each authentication method. 4mhost_based_auth_proc0m Host based authentication callback. 4mprotocol_setup_proc0m A callback to be invoked when authentication has succeeded for a 4mProtocolSetup24m but before the 4mPro-0m 4mtocolReply24m is sent. 4mprotocol_activate_proc0m A callback to be invoked after the 4mProtocolReply0m - 5 - 1mInter-Client Exchange Library X11, Release 6.40m is sent. 4mio_error_proc0m IO error handler, or NULL. |__ 4mIceRegisterForProtocolReply24m returns the major opcode reserved or -1 if an error occurred. The major opcode should be used in all subsequent messages sent for this pro- tocol. A protocol library may support multiple versions of the same protocol. The version_recs argument specifies a list of supported versions of the protocol, which are prioritized in decreasing order of preference. Each version record con- sists of a major and minor version of the protocol as well as a callback to be used for processing incoming messages. __ | typedef struct { int major_version; int minor_version; IcePaProcessMsgProc process_msg_proc; } IcePaVersionRec; |__ The 4mIcePaProcessMsgProc24m callback is responsible for process- ing the set of messages that can be received by the client that accepted the 4mProtocolSetup24m. For further information, see section 6.1, ``Callbacks for Processing Messages.'' Authentication may be required before the protocol can become active. The protocol library must register the authentication methods that it supports with the ICE library. The auth_names and auth_procs arguments are a list of authentication names and callbacks that are prioritized in decreasing order of preference. For information on the 4mIcePaAuthProc24m callback, see section 6.2, ``Authentication Methods.'' If authentication fails and the client attempting to initi- ate the 4mProtocolSetup24m has not required authentication, the 4mIceHostBasedAuthProc24m callback is invoked with the host name of the originating client. If the callback returns 4mTrue24m, the 4mProtocolSetup24m will succeed, even though the original authentication failed. Note that authentication can effec- tively be disabled by registering an 4mIceHostBasedAuthProc24m, which always returns 4mTrue24m. If no host based authentication is allowed, you should pass NULL for host_based_auth_proc. - 6 - 1mInter-Client Exchange Library X11, Release 6.40m __ | typedef Bool (*IceHostBasedAuthProc) (); Bool HostBasedAuthProc(4mhost_name24m) char *4mhost_name24m; 4mhost_name24m The host name of the client that sent the 4mProto-0m 4mcolSetup24m. |__ The host_name argument is a string of the form 4mproto-0m 4mcol24m/4mhostname24m, where 4mprotocol24m is one of {tcp, decnet, local}. Because 4mProtocolSetup24m messages and authentication happen behind the scenes via callbacks, the protocol library needs some way of being notified when the 4mProtocolSetup24m has com- pleted. This occurs in two phases. In the first phase, the 4mIceProtocolSetupProc24m callback is invoked after authentica- tion has successfully completed but before the ICE library sends a 4mProtocolReply24m. Any resources required for this pro- tocol should be allocated at this time. If the 4mIceProto-0m 4mcolSetupProc24m returns a successful status, the ICE library will send the 4mProtocolReply24m and then invoke the 4mIceProtoco-0m 4mlActivateProc24m callback. Otherwise, an error will be sent to the other client in response to the 4mProtocolSetup24m. The 4mIceProtocolActivateProc24m is an optional callback and should be registered only if the protocol library intends to generate a message immediately following the 4mProtocolReply24m. You should pass NULL for protocol_activate_proc if not interested in this callback. __ | typedef Status (*IceProtocolSetupProc) (); Status ProtocolSetupProc(4mice_conn24m, 4mmajor_version24m, 4mminor_version24m, 4mvendor24m, 4mrelease24m, 4mclient_data_ret24m, 4mfailure_reason_ret24m) IceConn 4mice_conn24m; int 4mmajor_version24m; int 4mminor_version24m; char *4mvendor24m; char *4mrelease24m; IcePointer *4mclient_data_ret24m; char **4mfailure_reason_ret24m; 4mice_conn24m The ICE connection object. 4mmajor_version0m The major version of the protocol. 4mminor_version0m The minor version of the protocol. - 7 - 1mInter-Client Exchange Library X11, Release 6.40m 4mvendor24m The vendor string registered by the protocol orig- inator. 4mrelease24m The release string registered by the protocol originator. 4mclient_data_ret0m Client data to be set by callback. 4mfailure_reason_ret0m Failure reason returned. |__ The pointer stored in the client_data_ret argument will be passed to the 4mIcePaProcessMsgProc24m callback whenever a mes- sage has arrived for this protocol on the ICE connection. The vendor and release strings should be freed with 4mfree0m when they are no longer needed. If a failure occurs, the 4mIceProtocolSetupProc24m should return a zero status as well as allocate and return a failure rea- son string in failure_reason_ret. The ICE library will be responsible for freeing this memory. The 4mIceProtocolActivateProc24m callback is defined as follows: __ | typedef void (*IceProtocolActivateProc)(); void ProtocolActivateProc(4mice_conn24m, 4mclient_data24m) IceConn 4mice_conn24m; IcePointer 4mclient_data24m; 4mice_conn24m The ICE connection object. 4mclient_data0m The client data set in the 4mIceProtocolSetupProc0m callback. |__ The 4mIceIOErrorProc24m callback is invoked if the ICE connection unexpectedly breaks. You should pass NULL for io_error_proc if not interested in being notified. For further informa- tion, see section 13, ``Error Handling.'' 1m6.1. Callbacks for Processing Messages0m When an application detects that there is new data to read on an ICE connection (via 4mselect24m), it calls the 4mIcePro-0m 4mcessMessages24m function (see section 9, ``Processing Mes- sages''). When 4mIceProcessMessages24m reads an ICE message header with a major opcode other than zero (reserved for the - 8 - 1mInter-Client Exchange Library X11, Release 6.40m ICE protocol), it needs to call a function that will read the rest of the message, unpack it, and process it accord- ingly. If the message arrives at the client that initiated the 4mPro-0m 4mtocolSetup24m, the 4mIcePoProcessMsgProc24m callback is invoked. __ | typedef void (*IcePoProcessMsgProc)(); void PoProcessMsgProc(4mice_conn24m, 4mclient_data24m, 4mopcode24m, 4mlength24m, 4mswap24m, 4mreply_wait24m, 4mreply_ready_ret24m) IceConn 4mice_conn24m; IcePointer 4mclient_data24m; int 4mopcode24m; unsigned long 4mlength24m; Bool 4mswap24m; IceReplyWaitInfo *4mreply_wait24m; Bool *4mreply_ready_ret24m; 4mice_conn24m The ICE connection object. 4mclient_data0m Client data associated with this protocol on the ICE connection. 4mopcode24m The minor opcode of the message. 4mlength24m The length (in 8-byte units) of the message beyond the ICE header. 4mswap24m A flag that indicates if byte swapping is neces- sary. 4mreply_wait0m Indicates if the invoking client is waiting for a reply. 4mreply_ready_ret0m If set to 4mTrue24m, a reply is ready. |__ If the message arrives at the client that accepted the 4mPro-0m 4mtocolSetup24m, the 4mIcePaProcessMsgProc24m callback is invoked. __ | - 9 - 1mInter-Client Exchange Library X11, Release 6.40m typedef void (*IcePaProcessMsgProc)(); void PaProcessMsgProc(4mice_conn24m, 4mclient_data24m, 4mopcode24m, 4mlength24m, 4mswap24m) IceConn 4mice_conn24m; IcePointer 4mclient_data24m; int 4mopcode24m; unsigned long 4mlength24m; Bool 4mswap24m; 4mice_conn24m The ICE connection object. 4mclient_data0m Client data associated with this protocol on the ICE connection. 4mopcode24m The minor opcode of the message. 4mlength24m The length (in 8-byte units) of the message beyond the ICE header. 4mswap24m A flag that indicates if byte swapping is neces- sary. |__ In order to read the message, both of these callbacks should use the macros defined for this purpose (see section 12.2, ``Reading ICE Messages''). Note that byte swapping may be necessary. As a convenience, the length field in the ICE header will be swapped by ICElib if necessary. In both of these callbacks, the client_data argument is a pointer to client data that was registered at 4mProtocolSetup0m time. In the case of 4mIcePoProcessMsgProc24m, the client data was set in the call to 4mIceProtocolSetup24m. In the case of 4mIcePaProcessMsgProc24m, the client data was set in the 4mIcePro-0m 4mtocolSetupProc24m callback. The 4mIcePoProcessMsgProc24m callback needs to check the reply_wait argument. If reply_wait is NULL , the ICE library expects the function to pass the message to the client via a callback. For example, if this is a Session Management ``Save Yourself'' message, this function should notify the client of the ``Save Yourself'' via a callback. The details of how such a callback would be defined are implementation-dependent. However, if reply_wait is not NULL , then the client is waiting for a reply or an error for a message it previously sent. The reply_wait is of type 4mIceReplyWaitInfo24m. __ | typedef struct { unsigned long sequence_of_request; - 10 - 1mInter-Client Exchange Library X11, Release 6.40m int major_opcode_of_request; int minor_opcode_of_request; IcePointer reply; } IceReplyWaitInfo; |__ 4mIceReplyWaitInfo24m contains the major/minor opcodes and sequence number of the message for which a reply is being awaited. It also contains a pointer to the reply message to be filled in (the protocol library should cast this 4mIce-0m 4mPointer24m to the appropriate reply type). In most cases, the reply will have some fixed-size part, and the client waiting for the reply will have provided a pointer to a structure to hold this fixed-size data. If there is variable-length data, it would be expected that the 4mIcePoProcessMsgProc0m callback will have to allocate additional memory and store pointer(s) to that memory in the fixed-size structure. If the entire data is variable length (for example., a single variable-length string), then the client waiting for the reply would probably just pass a pointer to fixed-size space to hold a pointer, and the 4mIcePoProcessMsgProc24m callback would allocate the storage and store the pointer. It is the responsibility of the client receiving the reply to free any memory allocated on its behalf. If reply_wait is not NULL and 4mIcePoProcessMsgProc24m has a reply or error to return in response to this reply_wait (that is, no callback was generated), then the reply_ready_ret argument should be set to 4mTrue24m. Note that an error should only be returned if it corresponds to the reply being waited for. Otherwise, the 4mIcePoProcessMsgProc0m should either handle the error internally or invoke an error handler for its library. If reply_wait is NULL, then care must be taken not to store any value in reply_ready_ret, because this pointer may also be NULL. The 4mIcePaProcessMsgProc24m callback, on the other hand, should always pass the message to the client via a callback. For example, if this is a Session Management ``Interact Request'' message, this function should notify the client of the ``Interact Request'' via a callback. The reason the 4mIcePaProcessMsgProc24m callback does not have a reply_wait, like 4mIcePoProcessMsgProc24m does, is because a process that is acting as a server should never block for a reply (infinite blocking can occur if the connecting client does not act properly, denying access to other clients). - 11 - 1mInter-Client Exchange Library X11, Release 6.40m 1m6.2. Authentication Methods0m As already stated, a protocol library must register the authentication methods that it supports with the ICE library. For each authentication method, there are two callbacks that may be registered: · One to handle the side that initiates a 4mProtocolSetup0m · One to handle the side that accepts or rejects this request 4mIcePoAuthProc24m is the callback invoked for the client that initiated the 4mProtocolSetup24m. This callback must be able to respond to the initial ``Authentication Required'' message or subsequent ``Authentication Next Phase'' messages sent by the other client. __ | typedef IcePoAuthStatus (*IcePoAuthProc)(); IcePoAuthStatus PoAuthProc(4mice_conn24m, 4mauth_state_ptr24m, 4mclean_up24m, 4mswap24m, 4mauth_datalen24m, 4mauth_data24m, 4mreply_datalen_ret24m, 4mreply_data_ret24m, 4merror_string_ret24m) IceConn 4mice_conn24m; IcePointer *4mauth_state_ptr24m; Bool 4mclean_up24m; Bool 4mswap24m; int 4mauth_datalen24m; IcePointer 4mauth_data24m; int *4mreply_datalen_ret24m; IcePointer *4mreply_data_ret24m; char **4merror_string_ret24m; 4mice_conn24m The ICE connection object. 4mauth_state_ptr0m A pointer to state for use by the authentication callback procedure. 4mclean_up24m If 4mTrue24m, authentication is over, and the function should clean up any state it was maintaining. The last 6 arguments should be ignored. 4mswap24m If 4mTrue24m, the auth_data may have to be byte swapped (depending on its contents). 4mauth_datalen0m The length (in bytes) of the authenticator data. 4mauth_data24m The data from the authenticator. 4mreply_datalen_ret0m The length (in bytes) of the reply data returned. - 12 - 1mInter-Client Exchange Library X11, Release 6.40m 4mreply_data_ret0m The reply data returned. 4merror_string_ret0m If the authentication procedure encounters an error during authentication, it should allocate and return an error string. |__ Authentication may require several phases, depending on the authentication method. As a result, the 4mIcePoAuthProc24m may be called more than once when authenticating a client, and some state will have to be maintained between each invoca- tion. At the start of each 4mProtocolSetup24m, *auth_state_ptr is NULL, and the function should initialize its state and set this pointer. In subsequent invocations of the call- back, the pointer should be used to get at any state previ- ously stored by the callback. If needed, the network ID of the client accepting the 4mProto-0m 4mcolSetup24m can be obtained by calling the 4mIceConnectionString0m function. ICElib will be responsible for freeing the reply_data_ret and error_string_ret pointers with 4mfree24m. The auth_data pointer may point to a volatile block of mem- ory. If the data must be kept beyond this invocation of the callback, be sure to make a copy of it. The 4mIcePoAuthProc24m should return one of four values: · 4mIcePoAuthHaveReply24m - a reply is available. · 4mIcePoAuthRejected24m - authentication rejected. · 4mIcePoAuthFailed24m - authentication failed. · 4mIcePoAuthDoneCleanup24m - done cleaning up. 4mIcePaAuthProc24m is the callback invoked for the client that received the 4mProtocolSetup24m. __ | - 13 - 1mInter-Client Exchange Library X11, Release 6.40m typedef IcePaAuthStatus (*IcePaAuthProc) (); IcePaAuthStatus PaAuthProc(4mice_conn24m, 4mauth_state_ptr24m, 4mswap24m, 4mauth_datalen24m, 4mauth_data24m, 4mreply_datalen_ret24m, 4mreply_data_ret24m, 4merror_string_ret24m) IceConn 4mice_conn24m; IcePointer *4mauth_state_ptr24m; Bool 4mswap24m; int 4mauth_datalen24m; IcePointer 4mauth_data24m; int *4mreply_datalen_ret24m; IcePointer *4mreply_data_ret24m; char **4merror_string_ret24m; 4mice_conn24m The ICE connection object. 4mauth_state_ptr0m A pointer to state for use by the authentication callback procedure. 4mswap24m If 4mTrue24m, auth_data may have to be byte swapped (depending on its contents). 4mauth_datalen0m The length (in bytes) of the protocol originator authentication data. 4mauth_data24m The authentication data from the protocol origina- tor. 4mreply_datalen_ret0m The length of the authentication data returned. 4mreply_data_ret0m The authentication data returned. 4merror_string_ret0m If authentication is rejected or fails, an error string is returned. |__ Authentication may require several phases, depending on the authentication method. As a result, the 4mIcePaAuthProc24m may be called more than once when authenticating a client, and some state will have to be maintained between each invoca- tion. At the start of each 4mProtocolSetup24m, auth_datalen is zero, *auth_state_ptr is NULL, and the function should ini- tialize its state and set this pointer. In subsequent invo- cations of the callback, the pointer should be used to get at any state previously stored by the callback. If needed, the network ID of the client accepting the 4mProto-0m 4mcolSetup24m can be obtained by calling the 4mIceConnectionString0m - 14 - 1mInter-Client Exchange Library X11, Release 6.40m function. The auth_data pointer may point to a volatile block of mem- ory. If the data must be kept beyond this invocation of the callback, be sure to make a copy of it. ICElib will be responsible for transmitting and freeing the reply_data_ret and error_string_ret pointers with 4mfree24m. The 4mIcePaAuthProc24m should return one of four values: · 4mIcePaAuthContinue24m - continue (or start) authentication. · 4mIcePaAuthAccepted24m - authentication accepted. · 4mIcePaAuthRejected24m - authentication rejected. · 4mIcePaAuthFailed24m - authentication failed. 1m7. ICE Connections0m In order for two clients to establish an ICE connection, one client has to be waiting for connections, and the other client has to initiate the connection. Most clients will initiate connections, so we discuss that first. 1m7.1. Opening an ICE Connection0m To open an ICE connection with another client (that is, waiting for connections), use 4mIceOpenConnection24m. __ | IceConn IceOpenConnection(4mnetwork_ids_list24m, 4mcontext24m, 4mmust_authenticate24m, 4mmajor_opcode_check24m, 4merror_length24m, 4merror_string_ret24m) char *4mnetwork_ids_list24m; IcePointer 4mcontext24m; Bool 4mmust_authenticate24m; int 4mmajor_opcode_check24m; int 4merror_length24m; char *4merror_string_ret24m; 4mnetwork_ids_list0m Specifies the network ID(s) of the other client. 4mcontext24m A pointer to an opaque object or NULL. Used to determine if an ICE connection can be shared (see below). 4mmust_authenticate0m If 4mTrue24m, the other client may not bypass authenti- cation. - 15 - 1mInter-Client Exchange Library X11, Release 6.40m 4mmajor_opcode_check0m Used to force a new ICE connection to be created (see below). 4merror_length0m Length of the error_string_ret argument passed in. 4merror_string_ret0m Returns a null-terminated error message, if any. The error_string_ret argument points to user sup- plied memory. No more than error_length bytes are used. |__ 4mIceOpenConnection24m returns an opaque ICE connection object if it succeeds; otherwise, it returns NULL. The network_ids_list argument contains a list of network IDs separated by commas. An attempt will be made to use the first network ID. If that fails, an attempt will be made using the second network ID, and so on. Each network ID has the following format: tcp/: or decnet/:: or local/: Most protocol libraries will have some sort of open function that should internally make a call into 4mIceOpenConnection24m. When 4mIceOpenConnection24m is called, it may be possible to use a previously opened ICE connection (if the target client is the same). However, there are cases in which shared ICE connections are not desired. The context argument is used to determine if an ICE connec- tion can be shared. If context is NULL, then the caller is always willing to share the connection. If context is not NULL, then the caller is not willing to use a previously opened ICE connection that has a different non-NULL context associated with it. In addition, if major_opcode_check contains a nonzero major opcode value, a previously created ICE connection will be used only if the major opcode is not active on the connec- tion. This can be used to force multiple ICE connections between two clients for the same protocol. Any authentication requirements are handled internally by the ICE library. The method by which the authentication data is obtained is implementation-dependent.- ----------- - The X Consortium's ICElib implementation uses an .ICEauthority file (see Appendix A). - 16 - 1mInter-Client Exchange Library X11, Release 6.40m After 4mIceOpenConnection24m is called, the client is ready to send a 4mProtocolSetup24m (provided that 4mIceRegisterForProto-0m 4mcolSetup24m was called) or receive a 4mProtocolSetup24m (provided that 4mIceRegisterForProtocolReply24m was called). 1m7.2. Listening for ICE Connections0m Clients wishing to accept ICE connections must first call 4mIceListenForConnections24m or 4mIceListenForWellKnownConnections0m so that they can listen for connections. A list of opaque "listen" objects are returned, one for each type of trans- port method that is available (for example, Unix Domain, TCP, DECnet, and so on). Normally clients will let ICElib allocate an available name in each transport and return listen objects. Such a client will then use 4mIceComposeNetworkIdList24m to extract the chosen names and make them available to other clients for opening the connection. In certain cases it may be necessary for a client to listen for connections on pre-arranged transport object names. Such a client may use 4mIceListenForWellKnown-0m 4mConnections24m to specify the names for the listen objects. __ | Status IceListenForConnections(4mcount_ret24m, 4mlisten_objs_ret24m, 4merror_length24m, 4merror_string_ret24m) int *4mcount_ret24m; IceListenObj **4mlisten_objs_ret24m; int 4merror_length24m; char *4merror_string_ret24m; 4mcount_ret24m Returns the number of listen objects created. 4mlisten_objs_ret0m Returns a list of pointers to opaque listen objects. 4merror_length0m The length of the error_string_ret argument passed in. 4merror_string_ret0m Returns a null-terminated error message, if any. The error_string_ret points to user supplied mem- ory. No more than error_length bytes are used. |__ The return value of 4mIceListenForConnections24m is zero for failure and a positive value for success. __ | - 17 - 1mInter-Client Exchange Library X11, Release 6.40m Status IceListenForWellKnownConnections(4mport_id24m, 4mcount_ret24m, 4mlisten_objs_ret24m, 4merror_length24m, 4merror_string_ret24m) char *4mport_id24m; int *4mcount_ret24m; IceListenObj **4mlisten_objs_ret24m; int 4merror_length24m; char *4merror_string_ret24m; 4mport_id24m Specifies the port identification for the address(es) to be opened. The value must not con- tain the slash (``/'') or comma (``,'') character; these are reserved for future use. 4mcount_ret24m Returns the number of listen objects created. 4mlisten_objs_ret0m Returns a list of pointers to opaque listen objects. 4merror_length0m The length of the error_string_ret argument passed in. 4merror_string_ret0m Returns a null-terminated error message, if any. The error_string_ret points to user supplied mem- ory. No more than error_length bytes are used. |__ 4mIceListenForWellKnownConnections24m constructs a list of net- work IDs by prepending each known transport to port_id and then attempts to create listen objects for the result. Port_id is the portnumber, objname, or path portion of the ICE network ID. If a listen object for a particular network ID cannot be created the network ID is ignored. If no lis- ten objects are created 4mIceListenForWellKnownConnections0m returns failure. The return value of 4mIceListenForWellKnownConnections24m is zero for failure and a positive value for success. To close and free the listen objects, use 4mIceFreeListenObjs24m. __ | void IceFreeListenObjs(4mcount24m, 4mlisten_objs24m) int 4mcount24m; IceListenObj *4mlisten_objs24m; 4mcount24m The number of listen objects. - 18 - 1mInter-Client Exchange Library X11, Release 6.40m 4mlisten_objs0m The listen objects. |__ To detect a new connection on a listen object, use 4mselect24m on the descriptor associated with the listen object. To obtain the descriptor, use 4mIceGetListenConnectionNumber24m. __ | int IceGetListenConnectionNumber(4mlisten_obj24m) IceListenObj 4mlisten_obj24m; 4mlisten_obj0m The listen object. |__ To obtain the network ID string associated with a listen object, use 4mIceGetListenConnectionString24m. __ | char *IceGetListenConnectionString(4mlisten_obj24m) IceListenObj 4mlisten_obj24m; 4mlisten_obj0m The listen object. |__ A network ID has the following format: tcp/: or decnet/:: or local/: To compose a string containing a list of network IDs sepa- rated by commas (the format recognized by 4mIceOpenConnec-0m 4mtion24m), use 4mIceComposeNetworkIdList24m. __ | char *IceComposeNetworkIdList(4mcount24m, 4mlisten_objs24m) int 4mcount24m; IceListenObj *4mlisten_objs24m; - 19 - 1mInter-Client Exchange Library X11, Release 6.40m 4mcount24m The number of listen objects. 4mlisten_objs0m The listen objects. |__ 1m7.3. Host Based Authentication for ICE Connections0m If authentication fails when a client attempts to open an ICE connection and the initiating client has not required authentication, a host based authentication procedure may be invoked to provide a last chance for the client to connect. Each listen object has such a callback associated with it, and this callback is set using the 4mIceSetHostBasedAuthProc0m function. __ | void IceSetHostBasedAuthProc(4mlisten_obj24m, 4mhost_based_auth_proc24m) IceListenObj 4mlisten_obj24m; IceHostBasedAuthProc 4mhost_based_auth_proc24m; 4mlisten_obj0m The listen object. 4mhost_based_auth_proc0m The host based authentication procedure. |__ By default, each listen object has no host based authentica- tion procedure associated with it. Passing NULL for host_based_auth_proc turns off host based authentication if it was previously set. __ | typedef Bool (*IceHostBasedAuthProc) (); Bool HostBasedAuthProc(4mhost_name24m) char *4mhost_name24m; 4mhost_name24m The host name of the client that tried to open an ICE connection. |__ The host_name argument is a string in the form 4mproto-0m 4mcol24m/4mhostname24m, where 4mprotocol24m is one of {tcp, decnet, local}. If 4mIceHostBasedAuthProc24m returns 4mTrue24m, access will be granted, even though the original authentication failed. Note that authentication can effectively be disabled by reg- istering an 4mIceHostBasedAuthProc24m, which always returns 4mTrue24m. - 20 - 1mInter-Client Exchange Library X11, Release 6.40m Host based authentication is also allowed at 4mProtocolSetup0m time. The callback is specified in the 4mIceRegisterForProto-0m 4mcolReply24m function (see section 6, ``Protocol Registra- tion''). 1m7.4. Accepting ICE Connections0m After a connection attempt is detected on a listen object returned by 4mIceListenForConnections24m, you should call 4mIceAc-0m 4mceptConnection24m. This returns a new opaque ICE connection object. __ | IceConn IceAcceptConnection(4mlisten_obj24m, 4mstatus_ret24m) IceListenObj 4mlisten_obj24m; IceAcceptStatus *4mstatus_ret24m; 4mlisten_obj0m The listen object on which a new connection was detected. 4mstatus_ret0m Return status information. |__ The status_ret argument is set to one of the following val- ues: · 4mIceAcceptSuccess24m - the accept operation succeeded, and the function returns a new connection object. · 4mIceAcceptFailure24m - the accept operation failed, and the function returns NULL. · 4mIceAcceptBadMalloc24m - a memory allocation failed, and the function returns NULL. In general, to detect new connections, you should call 4mselect24m on the file descriptors associated with the listen objects. When a new connection is detected, the 4mIceAccept-0m 4mConnection24m function should be called. 4mIceAcceptConnection0m may return a new ICE connection that is in a pending state. This is because before the connection can become valid, authentication may be necessary. Because the ICE library cannot block and wait for the connection to become valid (infinite blocking can occur if the connecting client does not act properly), the application must wait for the connec- tion status to become valid. The following pseudo-code demonstrates how connections are accepted: - 21 - 1mInter-Client Exchange Library X11, Release 6.40m new_ice_conn = IceAcceptConnection (listen_obj, &accept_status); if (accept_status != IceAcceptSuccess) { close the file descriptor and return } status = IceConnectionStatus (new_ice_conn); time_start = time_now; while (status == IceConnectPending) { select() on {new_ice_conn, all open connections} for (each ice_conn in the list of open connections) if (data ready on ice_conn) { status = IceProcessMessages (ice_conn, NULL, NULL); if (status == IceProcessMessagesIOError) IceCloseConnection (ice_conn); } if (data ready on new_ice_conn) { /* * IceProcessMessages is called until the connection * is non-pending. Doing so handles the connection * setup request and any authentication requirements. */ IceProcessMessages (new_ice_conn, NULL, NULL); status = IceConnectionStatus (new_ice_conn); } else { if (time_now - time_start > MAX_WAIT_TIME) status = IceConnectRejected; } } if (status == IceConnectAccepted) { Add new_ice_conn to the list of open connections } else { IceCloseConnection (new_ice_conn); } After 4mIceAcceptConnection24m is called and the connection has been validated, the client is ready to receive a 4mProto-0m 4mcolSetup24m (provided that 4mIceRegisterForProtocolReply24m was called) or send a 4mProtocolSetup24m (provided that 4mIceRegister-0m 4mForProtocolSetup24m was called). - 22 - 1mInter-Client Exchange Library X11, Release 6.40m 1m7.5. Closing ICE Connections0m To close an ICE connection created with 4mIceOpenConnection24m or 4mIceAcceptConnection24m, use 4mIceCloseConnection24m. __ | IceCloseStatus IceCloseConnection(4mice_conn24m) IceConn 4mice_conn24m; 4mice_conn24m The ICE connection to close. |__ To actually close an ICE connection, the following condi- tions must be met: · The 4mopen24m 4mreference24m 4mcount24m must have reached zero on this ICE connection. When 4mIceOpenConnection24m is called, it tries to use a previously opened ICE connection. If it is able to use an existing connection, it increments the open reference count on the connection by one. So, to close an ICE connection, each call to 4mIceOpenConnec-0m 4mtion24m must be matched with a call to 4mIceCloseConnection24m. The connection can be closed only on the last call to 4mIceCloseConnection24m. · The 4mactive24m 4mprotocol24m 4mcount24m must have reached zero. Each time a 4mProtocolSetup24m succeeds on the connection, the active protocol count is incremented by one. When the client no longer expects to use the protocol on the connection, the 4mIceProtocolShutdown24m function should be called, which decrements the active protocol count by one (see section 8, ``Protocol Setup and Shutdown''). · If shutdown negotiation is enabled on the connection, the client on the other side of the ICE connection must agree to have the connection closed. 4mIceCloseConnection24m returns one of the following values: · 4mIceClosedNow24m - the ICE connection was closed at this time. The watch procedures were invoked and the con- nection was freed. · 4mIceClosedASAP24m - an IO error had occurred on the connec- tion, but 4mIceCloseConnection24m is being called within a nested 4mIceProcessMessages24m. The watch procedures have been invoked at this time, but the connection will be freed as soon as possible (when the nesting level reaches zero and 4mIceProcessMessages24m returns a status of 4mIceProcessMessagesConnectionClosed24m). · 4mIceConnectionInUse24m - the connection was not closed at this time, because it is being used by other active - 23 - 1mInter-Client Exchange Library X11, Release 6.40m protocols. · 4mIceStartedShutdownNegotiation24m - the connection was not closed at this time and shutdown negotiation started with the client on the other side of the ICE connec- tion. When the connection is actually closed, 4mIcePro-0m 4mcessMessages24m will return a status of 4mIceProcessMes-0m 4msagesConnectionClosed24m. When it is known that the client on the other side of the ICE connection has terminated the connection without initi- ating shutdown negotiation, the 4mIceSetShutdownNegotiation0m function should be called to turn off shutdown negotiation. This will prevent 4mIceCloseConnection24m from writing to a bro- ken connection. __ | void IceSetShutdownNegotiation(4mice_conn24m, 4mnegotiate24m) IceConn 4mice_conn24m; Bool 4mnegotiate24m; 4mice_conn24m A valid ICE connection object. 4mnegotiate24m If 4mFalse24m, shutdown negotiating will be turned off. |__ To check the shutdown negotiation status of an ICE connec- tion, use 4mIceCheckShutdownNegotiation24m. __ | Bool IceCheckShutdownNegotiation(4mice_conn24m) IceConn 4mice_conn24m; 4mice_conn24m A valid ICE connection object. |__ 4mIceCheckShutdownNegotiation24m returns 4mTrue24m if shutdown negoti- ation will take place on the connection; otherwise, it returns 4mFalse24m. Negotiation is on by default for a connec- tion. It can only be changed with the 4mIceSetShutdownNegoti-0m 4mation24m function. 1m7.6. Connection Watch Procedures0m To add a watch procedure that will be called each time ICElib opens a new connection via 4mIceOpenConnection24m or 4mIceAcceptConnection24m or closes a connection via 4mIceCloseCon-0m - 24 - 1mInter-Client Exchange Library X11, Release 6.40m 4mnection24m, use 4mIceAddConnectionWatch24m. __ | Status IceAddConnectionWatch(4mwatch_proc24m, 4mclient_data24m) IceWatchProc 4mwatch_proc24m; IcePointer 4mclient_data24m; 4mwatch_proc0m The watch procedure to invoke when ICElib opens or closes a connection. 4mclient_data0m This pointer will be passed to the watch proce- dure. |__ The return value of 4mIceAddConnectionWatch24m is zero for fail- ure, and a positive value for success. Note that several calls to 4mIceOpenConnection24m might share the same ICE connection. In such a case, the watch procedure is only invoked when the connection is first created (after authentication succeeds). Similarly, because connections might be shared, the watch procedure is called only if 4mIce-0m 4mCloseConnection24m actually closes the connection (right before the IceConn is freed). The watch procedures are very useful for applications that need to add a file descriptor to a select mask when a new connection is created and remove the file descriptor when the connection is destroyed. Because connections are shared, knowing when to add and remove the file descriptor from the select mask would be difficult without the watch procedures. Multiple watch procedures may be registered with the ICE library. No assumptions should be made about their order of invocation. If one or more ICE connections were already created by the ICE library at the time the watch procedure is registered, the watch procedure will instantly be invoked for each of these ICE connections (with the opening argument set to 4mTrue24m). The watch procedure is of type 4mIceWatchProc24m. __ | - 25 - 1mInter-Client Exchange Library X11, Release 6.40m typedef void (*IceWatchProc)(); void WatchProc(4mice_conn24m, 4mclient_data24m, 4mopening24m, 4mwatch_data24m) IceConn 4mice_conn24m; IcePointer 4mclient_data24m; Bool 4mopening24m; IcePointer *4mwatch_data24m; 4mice_conn24m The opened or closed ICE connection. Call 4mIceCon-0m 4mnectionNumber24m to get the file descriptor associ- ated with this connection. 4mclient_data0m Client data specified in the call to 4mIceAddConnec-0m 4mtionWatch24m. 4mopening24m If 4mTrue24m, the connection is being opened. If 4mFalse24m, the connection is being closed. 4mwatch_data0m Can be used to save a pointer to client data. |__ If opening is 4mTrue24m, the client should set the *watch_data pointer to any data it may need to save until the connection is closed and the watch procedure is invoked again with opening set to 4mFalse24m. To remove a watch procedure, use 4mIceRemoveConnectionWatch24m. __ | void IceRemoveConnectionWatch(4mwatch_proc24m, 4mclient_data24m) IceWatchProc 4mwatch_proc24m; IcePointer 4mclient_data24m; 4mwatch_proc0m The watch procedure that was passed to 4mIceAddCon-0m 4mnectionWatch24m. 4mclient_data0m The client_data pointer that was passed to 4mIceAdd-0m 4mConnectionWatch24m. |__ 1m8. Protocol Setup and Shutdown0m To activate a protocol on a given ICE connection, use 4mIce-0m 4mProtocolSetup24m. - 26 - 1mInter-Client Exchange Library X11, Release 6.40m __ | IceProtocolSetupStatus IceProtocolSetup(4mice_conn24m, 4mmy_opcode24m, 4mclient_data24m, 4mmust_authenticate24m, 4mmajor_version_ret24m, 4mminor_version_ret24m, 4mvendor_ret24m, 4mrelease_ret24m, 4merror_length24m, 4merror_string_ret24m) IceConn 4mice_conn24m; int 4mmy_opcode24m; IcePointer 4mclient_data24m; Bool 4mmust_authenticate24m; int *4mmajor_version_ret24m; int *4mminor_version_ret24m; char **4mvendor_ret24m; char **4mrelease_ret24m; int 4merror_length24m; char *4merror_string_ret24m; 4mice_conn24m A valid ICE connection object. 4mmy_opcode24m The major opcode of the protocol to be set up, as returned by 4mIceRegisterForProtocolSetup24m. 4mclient_data0m The client data stored in this pointer will be passed to the 4mIcePoProcessMsgProc24m callback. 4mmust_authenticate0m If 4mTrue24m, the other client may not bypass authenti- cation. 4mmajor_version_ret0m The major version of the protocol to be used is returned. 4mminor_version_ret0m The minor version of the protocol to be used is returned. 4mvendor_ret0m The vendor string specified by the protocol accep- tor. 4mrelease_ret0m The release string specified by the protocol acceptor. 4merror_length0m Specifies the length of the error_string_ret argu- ment passed in. 4merror_string_ret0m Returns a null-terminated error message, if any. The error_string_ret argument points to user sup- plied memory. No more than error_length bytes are used. - 27 - 1mInter-Client Exchange Library X11, Release 6.40m |__ The vendor_ret and release_ret strings should be freed with 4mfree24m when no longer needed. 4mIceProtocolSetup24m returns one of the following values: · 4mIceProtocolSetupSuccess24m - the major_version_ret, minor_version_ret, vendor_ret, release_ret are set. · 4mIceProtocolSetupFailure24m or 4mIceProtocolSetupIOError24m - check error_string_ret for failure reason. The major_version_ret, minor_version_ret, vendor_ret, release_ret are not set. · 4mIceProtocolAlreadyActive24m - this protocol is already active on this connection. The major_version_ret, minor_version_ret, vendor_ret, release_ret are not set. To notify the ICE library when a given protocol will no longer be used on an ICE connection, use 4mIceProtocolShut-0m 4mdown24m. __ | Status IceProtocolShutdown(4mice_conn24m, 4mmajor_opcode24m) IceConn 4mice_conn24m; int 4mmajor_opcode24m; 4mice_conn24m A valid ICE connection object. 4mmajor_opcode0m The major opcode of the protocol to shut down. |__ The return value of 4mIceProtocolShutdown24m is zero for failure and a positive value for success. Failure will occur if the major opcode was never registered OR the protocol of the major opcode was never activated on the connection. By activated, we mean that a 4mProtocolSetup0m succeeded on the connection. Note that ICE does not define how each sub-protocol triggers a protocol shutdown. 1m9. Processing Messages0m To process incoming messages on an ICE connection, use 4mIce-0m 4mProcessMessages24m. __ | - 28 - 1mInter-Client Exchange Library X11, Release 6.40m IceProcessMessagesStatus IceProcessMessages(4mice_conn24m, 4mreply_wait24m, 4mreply_ready_ret24m) IceConn 4mice_conn24m; IceReplyWaitInfo *4mreply_wait24m; Bool *4mreply_ready_ret24m; 4mice_conn24m A valid ICE connection object. 4mreply_wait0m Indicates if a reply is being waited for. 4mreply_ready_ret0m If set to 4mTrue24m on return, a reply is ready. |__ 4mIceProcessMessages24m is used in two ways: · In the first, a client may generate a message and block by calling 4mIceProcessMessages24m repeatedly until it gets its reply. · In the second, a client calls 4mIceProcessMessages24m with reply_wait set to NULL in response to 4mselect24m showing that there is data to read on the ICE connection. The ICE library may process zero or more complete messages. Note that messages that are not blocked for are always processed by invoking callbacks. 4mIceReplyWaitInfo24m contains the major/minor opcodes and sequence number of the message for which a reply is being awaited. It also contains a pointer to the reply message to be filled in (the protocol library should cast this 4mIce-0m 4mPointer24m to the appropriate reply type). In most cases, the reply will have some fixed-size part, and the client waiting for the reply will have provided a pointer to a structure to hold this fixed-size data. If there is variable-length data, it would be expected that the 4mIcePoProcessMsgProc0m callback will have to allocate additional memory and store pointer(s) to that memory in the fixed-size structure. If the entire data is variable length (for example, a single variable-length string), then the client waiting for the reply would probably just pass a pointer to fixed-size space to hold a pointer, and the 4mIcePoProcessMsgProc24m callback would allocate the storage and store the pointer. It is the responsibility of the client receiving the reply to free up any memory allocated on its behalf. __ | typedef struct { unsigned long sequence_of_request; int major_opcode_of_request; int minor_opcode_of_request; IcePointer reply; - 29 - 1mInter-Client Exchange Library X11, Release 6.40m } IceReplyWaitInfo; |__ If reply_wait is not NULL and 4mIceProcessMessages24m has a reply or error to return in response to this reply_wait (that is, no callback was generated), then the reply_ready_ret argu- ment will be set to 4mTrue24m. If reply_wait is NULL, then the caller may also pass NULL for reply_ready_ret and be guaranteed that no value will be stored in this pointer. 4mIceProcessMessages24m returns one of the following values: · 4mIceProcessMessagesSuccess24m - no error occurred. · 4mIceProcessMessagesIOError24m - an IO error occurred, and the caller must explicitly close the connection by calling 4mIceCloseConnection24m. · 4mIceProcessMessagesConnectionClosed24m - the ICE connection has been closed (closing of the connection was deferred because of shutdown negotiation, or because the 4mIcePro-0m 4mcessMessages24m nesting level was not zero). Do not attempt to access the ICE connection at this point, since it has been freed. 1m10. Ping0m To send a ``Ping'' message to the client on the other side of the ICE connection, use 4mIcePing24m. __ | Status IcePing(4mice_conn24m, 4mping_reply_proc24m, 4mclient_data24m) IceConn 4mice_conn24m; IcePingReplyProc 4mping_reply_proc24m; IcePointer 4mclient_data24m; 4mice_conn24m A valid ICE connection object. 4mping_reply_proc0m The callback to invoke when the Ping reply arrives. 4mclient_data0m This pointer will be passed to the 4mIcePingRe-0m 4mplyProc24m callback. |__ 4mIcePing24m returns zero for failure and a positive value for success. - 30 - 1mInter-Client Exchange Library X11, Release 6.40m When 4mIceProcessMessages24m processes the Ping reply, it will invoke the 4mIcePingReplyProc24m callback. __ | typedef void (*IcePingReplyProc)(); void PingReplyProc(4mice_conn24m, 4mclient_data24m) IceConn 4mice_conn24m; IcePointer 4mclient_data24m; 4mice_conn24m The ICE connection object. 4mclient_data0m The client data specified in the call to 4mIcePing24m. |__ 1m11. Using ICElib Informational Functions0m __ | IceConnectStatus IceConnectionStatus(4mice_conn24m) IceConn 4mice_conn24m; |__ 4mIceConnectionStatus24m returns the status of an ICE connection. The possible return values are: · 4mIceConnectPending24m - the connection is not valid yet (that is, authentication is taking place). This is only relevant to connections created by 4mIceAcceptCon-0m 4mnection24m. · 4mIceConnectAccepted24m - the connection has been accepted. This is only relevant to connections created by 4mIceAc-0m 4mceptConnection24m. · 4mIceConnectRejected24m - the connection had been rejected (that is, authentication failed). This is only rele- vant to connections created by 4mIceAcceptConnection24m. · 4mIceConnectIOError24m - an IO error has occurred on the connection. __ | char *IceVendor(4mice_conn24m) IceConn 4mice_conn24m; |__ 4mIceVendor24m returns the ICE library vendor identification for the other side of the connection. The string should be freed with a call to 4mfree24m when no longer needed. - 31 - 1mInter-Client Exchange Library X11, Release 6.40m __ | char *IceRelease(4mice_conn24m) IceConn 4mice_conn24m; |__ 4mIceRelease24m returns the release identification of the ICE library on the other side of the connection. The string should be freed with a call to 4mfree24m when no longer needed. __ | int IceProtocolVersion(4mice_conn24m) IceConn 4mice_conn24m; |__ 4mIceProtocolVersion24m returns the major version of the ICE pro- tocol on this connection. __ | int IceProtocolRevision(4mice_conn24m) IceConn 4mice_conn24m; |__ 4mIceProtocolRevision24m returns the minor version of the ICE protocol on this connection. __ | int IceConnectionNumber(4mice_conn24m) IceConn 4mice_conn24m; |__ 4mIceConnectionNumber24m returns the file descriptor of this ICE connection. __ | char *IceConnectionString(4mice_conn24m) IceConn 4mice_conn24m; |__ 4mIceConnectionString24m returns the network ID of the client that accepted this connection. The string should be freed with a call to 4mfree24m when no longer needed. __ | unsigned long IceLastSentSequenceNumber(4mice_conn24m) IceConn 4mice_conn24m; |__ 4mIceLastSentSequenceNumber24m returns the sequence number of the last message sent on this ICE connection. - 32 - 1mInter-Client Exchange Library X11, Release 6.40m __ | unsigned long IceLastReceivedSequenceNumber(4mice_conn24m) IceConn 4mice_conn24m; |__ 4mIceLastReceivedSequenceNumber24m returns the sequence number of the last message received on this ICE connection. __ | Bool IceSwapping(4mice_conn24m) IceConn 4mice_conn24m; |__ 4mIceSwapping24m returns 4mTrue24m if byte swapping is necessary when reading messages on the ICE connection. __ | IcePointer IceGetContext(4mice_conn24m) IceConn 4mice_conn24m; |__ 4mIceGetContext24m returns the context associated with a connec- tion created by 4mIceOpenConnection24m. 1m12. ICE Messages0m All ICE messages have a standard 8-byte header. The ICElib macros that read and write messages rely on the following naming convention for message headers: CARD8major_opcode; CARD8minor_opcode; CARD8data[2]; CARD32length B32; The 3rd and 4th bytes of the message header can be used as needed. The length field is specified in units of 8 bytes. 1m12.1. Sending ICE Messages0m The ICE library maintains an output buffer used for generat- ing messages. Protocol libraries layered on top of ICE may choose to batch messages together and flush the output buffer at appropriate times. If an IO error has occurred on an ICE connection, all write operations will be ignored. For further information, see section 13, ``Error Handling.'' - 33 - 1mInter-Client Exchange Library X11, Release 6.40m To get the size of the ICE output buffer, use 4mIceGetOutBuf-0m 4mSize24m. __ | int IceGetOutBufSize(4mice_conn24m) IceConn 4mice_conn24m; 4mice_conn24m A valid ICE connection object. |__ To flush the ICE output buffer, use 4mIceFlush24m. __ | IceFlush(4mice_conn24m) IceConn 4mice_conn24m; 4mice_conn24m A valid ICE connection object. |__ Note that the output buffer may be implicitly flushed if there is insufficient space to generate a message. The following macros can be used to generate ICE messages: __ | IceGetHeader(4mice_conn24m, 4mmajor_opcode24m, 4mminor_opcode24m, 4mheader_size24m, 4m24m, 4mpmsg24m) IceConn 4mice_conn24m; int 4mmajor_opcode24m; int 4mminor_opcode24m; int 4mheader_size24m; *4mpmsg24m; 4mice_conn24m A valid ICE connection object. 4mmajor_opcode0m The major opcode of the message. 4mminor_opcode0m The minor opcode of the message. 4mheader_size0m The size of the message header (in bytes). 4m0m The actual C data type of the message header. 4mpmsg24m The message header pointer. After this macro is called, the library can store data in the message header. - 34 - 1mInter-Client Exchange Library X11, Release 6.40m |__ 4mIceGetHeader24m is used to set up a message header on an ICE connection. It sets the major and minor opcodes of the mes- sage, and initializes the message's length to the length of the header. If additional variable length data follows, the message's length field should be updated. __ | IceGetHeaderExtra(4mice_conn24m, 4mmajor_opcode24m, 4mminor_opcode24m, 4mheader_size24m, 4mextra24m, 4m24m, 4mpmsg24m, 4mpdata24m) IceConn 4mice_conn24m; int 4mmajor_opcode24m; int 4mminor_opcode24m; int 4mheader_size24m; int 4mextra24m; *4mpmsg24m; char *4mpdata24m; 4mice_conn24m A valid ICE connection object. 4mmajor_opcode0m The major opcode of the message. 4mminor_opcode0m The minor opcode of the message. 4mheader_size0m The size of the message header (in bytes). 4mextra24m The size of the extra data beyond the header (in 8-byte units). 4m0m The actual C data type of the message header. 4mpmsg24m The message header pointer. After this macro is called, the library can store data in the message header. 4mpdata24m Returns a pointer to the ICE output buffer that points immediately after the message header. The variable length data should be stored here. If there was not enough room in the ICE output buffer, pdata is set to NULL. |__ 4mIceGetHeaderExtra24m is used to generate a message with a fixed (and relatively small) amount of variable length data. The complete message must fit in the ICE output buffer. - 35 - 1mInter-Client Exchange Library X11, Release 6.40m __ | IceSimpleMessage(4mice_conn24m, 4mmajor_opcode24m, 4mminor_opcode24m) IceConn 4mice_conn24m; int 4mmajor_opcode24m; int 4mminor_opcode24m; 4mice_conn24m A valid ICE connection object. 4mmajor_opcode0m The major opcode of the message. 4mminor_opcode0m The minor opcode of the message. |__ 4mIceSimpleMessage24m is used to generate a message that is iden- tical in size to the ICE header message, and has no addi- tional data. __ | IceErrorHeader(4mice_conn24m, 4moffending_major_opcode24m, 4moffending_minor_opcode24m, 4moffending_sequence_num24m, 4mseverity24m, 4merror_class24m, 4mdata_length24m) IceConn 4mice_conn24m; int 4moffending_major_opcode24m; int 4moffending_minor_opcode24m; int 4moffending_sequence_num24m; int 4mseverity24m; int 4merror_class24m; int 4mdata_length24m; 4mice_conn24m A valid ICE connection object. 4moffending_major_opcode0m The major opcode of the protocol in which an error was detected. 4moffending_minor_opcode0m The minor opcode of the protocol in which an error was detected. 4moffending_sequence_num0m The sequence number of the message that caused the error. 4mseverity24m 4mIceCanContinue24m, 4mIceFatalToProtocol24m, or 4mIceFatalTo-0m 4mConnection24m. 4merror_class0m The error class. - 36 - 1mInter-Client Exchange Library X11, Release 6.40m 4mdata_length0m Length of data (in 8-byte units) to be written after the header. |__ 4mIceErrorHeader24m sets up an error message header. Note that the two clients connected by ICE may be using dif- ferent major opcodes for a given protocol. The offend- ing_major_opcode passed to this macro is the major opcode of the protocol for the client sending the error message. Generic errors, which are common to all protocols, have classes in the range 0x8000..0xFFFF. See the 4mInter-Client0m 4mExchange24m 4mProtocol24m standard for more details. 4mIceBadMi-24m 0x8000 4mnor0m 4mIceBad-24m 0x8001 4mState0m 4mIce-24m 0x8002 4mBadLength0m 4mIceBad-24m 0x8003 4mValue0m Per-protocol errors have classes in the range 0x0000-0x7fff. To write data to an ICE connection, use the 4mIceWriteData0m macro. If the data fits into the ICE output buffer, it is copied there. Otherwise, the ICE output buffer is flushed and the data is directly sent. This macro is used in conjunction with 4mIceGetHeader24m and 4mIceErrorHeader24m. __ | IceWriteData(4mice_conn24m, 4mbytes24m, 4mdata24m) IceConn 4mice_conn24m; int 4mbytes24m; char *4mdata24m; 4mice_conn24m A valid ICE connection object. 4mbytes24m The number of bytes to write. 4mdata24m The data to write. |__ - 37 - 1mInter-Client Exchange Library X11, Release 6.40m To write data as 16-bit quantities, use 4mIceWriteData1624m. __ | IceWriteData16(4mice_conn24m, 4mbytes24m, 4mdata24m) IceConn 4mice_conn24m; int 4mbytes24m; short *4mdata24m; 4mice_conn24m A valid ICE connection object. 4mbytes24m The number of bytes to write. 4mdata24m The data to write. |__ To write data as 32-bit quantities, use 4mIceWriteData3224m. __ | IceWriteData32(4mice_conn24m, 4mbytes24m, 4mdata24m) IceConn 4mice_conn24m; int 4mbytes24m; long *4mdata24m; 4mice_conn24m A valid ICE connection object. 4mbytes24m The number of bytes to write. 4mdata24m The data to write. |__ To bypass copying data to the ICE output buffer, use 4mIce-0m 4mSendData24m to directly send data over the network connection. If necessary, the ICE output buffer is first flushed. __ | IceSendData(4mice_conn24m, 4mbytes24m, 4m(char24m 4m*)24m 4mdata24m) IceConn 4mice_conn24m; int 4mbytes24m; char *4mdata24m; 4mice_conn24m A valid ICE connection object. 4mbytes24m The number of bytes to send. 4mdata24m The data to send. |__ To force 32-bit or 64-bit alignment, use 4mIceWritePad24m. A - 38 - 1mInter-Client Exchange Library X11, Release 6.40m maximum of 7 pad bytes can be specified. __ | IceWritePad(4mice_conn24m, 4mbytes24m) IceConn 4mice_conn24m; int 4mbytes24m; 4mice_conn24m A valid ICE connection object. 4mbytes24m The number of pad bytes. |__ 1m12.2. Reading ICE Messages0m The ICE library maintains an input buffer used for reading messages. If the ICE library chooses to perform nonblocking reads (this is implementation-dependent), then for every read operation that it makes, zero or more complete messages may be read into the input buffer. As a result, for all of the macros described in this section that read messages, an actual read operation will occur on the connection only if the data is not already present in the input buffer. To get the size of the ICE input buffer, use 4mIceGetInBuf-0m 4mSize24m. __ | int IceGetInBufSize(4mice_conn24m) IceConn 4mice_conn24m; 4mice_conn24m A valid ICE connection object. |__ When reading messages, care must be taken to check for IO errors. If any IO error occurs in reading any part of a message, the message should be thrown out. After using any of the macros described below for reading messages, the 4mIce-0m 4mValidIO24m macro can be used to check if an IO error occurred on the connection. After an IO error has occurred on an ICE connection, all read operations will be ignored. For fur- ther information, see section 13, ``Error Handling.'' __ | Bool IceValidIO(4mice_conn24m) IceConn 4mice_conn24m; - 39 - 1mInter-Client Exchange Library X11, Release 6.40m |__ The following macros can be used to read ICE messages. __ | IceReadSimpleMessage(4mice_conn24m, 4m24m, 4mpmsg24m) IceConn 4mice_conn24m; *4mpmsg24m; 4mice_conn24m A valid ICE connection object. 4m0m The actual C data type of the message header. 4mpmsg24m This pointer is set to the message header. |__ 4mIceReadSimpleMessage24m is used for messages that are identical in size to the 8-byte ICE header, but use the spare 2 bytes in the header to encode additional data. Note that the ICE library always reads in these first 8 bytes, so it can obtain the major opcode of the message. 4mIceReadSimpleMes-0m 4msage24m simply returns a pointer to these 8 bytes; it does not actually read any data into the input buffer. For a message with variable length data, there are two ways of reading the message. One method involves reading the complete message in one pass using 4mIceReadCompleteMessage24m. The second method involves reading the message header (note that this may be larger than the 8-byte ICE header), then reading the variable length data in chunks (see 4mIceReadMes-0m 4msageHeader24m and 4mIceReadData24m). __ | IceReadCompleteMessage(4mice_conn24m, 4mheader_size24m, 4m24m, 4mpmsg24m, 4mpdata24m) IceConn 4mice_conn24m; int 4mheader_size24m; *4mpmsg24m; char *4mpdata24m; 4mice_conn24m A valid ICE connection object. 4mheader_size0m The size of the message header (in bytes). 4m0m The actual C data type of the message header. - 40 - 1mInter-Client Exchange Library X11, Release 6.40m 4mpmsg24m This pointer is set to the message header. 4mpdata24m This pointer is set to the variable length data of the message. |__ If the ICE input buffer has sufficient space, 4mIceReadCom-0m 4mpleteMessage24m will read the complete message into the ICE input buffer. Otherwise, a buffer will be allocated to hold the variable length data. After the call, the pdata argu- ment should be checked against NULL to make sure that there was sufficient memory to allocate the buffer. After calling 4mIceReadCompleteMessage24m and processing the mes- sage, 4mIceDisposeCompleteMessage24m should be called. __ | IceDisposeCompleteMessage(4mice_conn24m, 4mpdata24m) IceConn 4mice_conn24m; char *4mpdata24m; 4mice_conn24m A valid ICE connection object. 4mpdata24m The pointer to the variable length data returned in 4mIceReadCompleteMessage24m. |__ If a buffer had to be allocated to hold the variable length data (because it did not fit in the ICE input buffer), it is freed here by ICElib. __ | IceReadMessageHeader(4mice_conn24m, 4mheader_size24m, 4m24m, 4mpmsg24m) IceConn 4mice_conn24m; int 4mheader_size24m; *4mpmsg24m; 4mice_conn24m A valid ICE connection object. 4mheader_size0m The size of the message header (in bytes). 4m0m The actual C data type of the message header. 4mpmsg24m This pointer is set to the message header. - 41 - 1mInter-Client Exchange Library X11, Release 6.40m |__ 4mIceReadMessageHeader24m reads just the message header. The rest of the data should be read with the 4mIceReadData24m family of macros. This method of reading a message should be used when the variable length data must be read in chunks. To read data directly into a user supplied buffer, use 4mIceReadData24m. __ | IceReadData(4mice_conn24m, 4mbytes24m, 4mpdata24m) IceConn 4mice_conn24m; int 4mbytes24m; char *4mpdata24m; 4mice_conn24m A valid ICE connection object. 4mbytes24m The number of bytes to read. 4mpdata24m The data is read into this user supplied buffer. |__ To read data as 16-bit quantities, use 4mIceReadData1624m. __ | IceReadData16(4mice_conn24m, 4mswap24m, 4mbytes24m, 4mpdata24m) IceConn 4mice_conn24m; Bool 4mswap24m; int 4mbytes24m; short *4mpdata24m; 4mice_conn24m A valid ICE connection object. 4mswap24m If 4mTrue,24m the values will be byte swapped. 4mbytes24m The number of bytes to read. 4mpdata24m The data is read into this user supplied buffer. |__ To read data as 32-bit quantities, use 4mIceReadData3224m. __ | - 42 - 1mInter-Client Exchange Library X11, Release 6.40m IceReadData32(4mice_conn24m, 4mswap24m, 4mbytes24m, 4mpdata24m) IceConn 4mice_conn24m; Bool 4mswap24m; int 4mbytes24m; long *4mpdata24m; 4mice_conn24m A valid ICE connection object. 4mswap24m If 4mTrue,24m the values will be byte swapped. 4mbytes24m The number of bytes to read. 4mpdata24m The data is read into this user supplied buffer. |__ To force 32-bit or 64-bit alignment, use 4mIceReadPad24m. A max- imum of 7 pad bytes can be specified. __ | IceReadPad(4mice_conn24m, 4mbytes24m) IceConn 4mice_conn24m; int 4mbytes24m; 4mice_conn24m A valid ICE connection object. 4mbytes24m The number of pad bytes. |__ 1m13. Error Handling0m There are two default error handlers in ICElib: · One to handle typically fatal conditions (for example, a connection dying because a machine crashed) · One to handle ICE-specific protocol errors These error handlers can be changed to user-supplied rou- tines if you prefer your own error handling and can be changed as often as you like. To set the ICE error handler, use 4mIceSetErrorHandler24m. __ | IceErrorHandler IceSetErrorHandler(4mhandler24m) IceErrorHandler 4mhandler24m; - 43 - 1mInter-Client Exchange Library X11, Release 6.40m 4mhandler24m The ICE error handler. You should pass NULL to restore the default handler. |__ 4mIceSetErrorHandler24m returns the previous error handler. The ICE error handler is invoked when an unexpected ICE pro- tocol error (major opcode 0) is encountered. The action of the default handler is to print an explanatory message to 4mstderr24m and if the severity is fatal, call 4mexit24m with a nonzero value. If exiting is undesirable, the application should register its own error handler. Note that errors in other protocol domains should be handled by their respective libraries (these libraries should have their own error handlers). An ICE error handler has the type of 4mIceErrorHandler24m. __ | typedef void (*IceErrorHandler)(); void ErrorHandler(4mice_conn24m, 4mswap24m, 4moffending_minor_opcode24m, 4moffending_sequence_num24m, 4merror_class24m, 4mseverity24m, 4mvalues24m) IceConn 4mice_conn24m; Bool 4mswap24m; int 4moffending_minor_opcode24m; unsigned long 4moffending_sequence_num24m; int 4merror_class24m; int 4mseverity24m; IcePointer 4mvalues24m; 4mice_conn24m The ICE connection object. 4mswap24m A flag that indicates if the values need byte swapping. 4moffending_minor_opcode0m The ICE minor opcode of the offending message. 4moffending_sequence_num0m The sequence number of the offending message. 4merror_class0m The error class of the offending message. 4mseverity24m 4mIceCanContinue24m, 4mIceFatalToProtocol24m, or 4mIceFatalTo-0m 4mConnection24m. 4mvalues24m Any additional error values specific to the minor opcode and class. - 44 - 1mInter-Client Exchange Library X11, Release 6.40m |__ The following error classes are defined at the ICE level: 4mIceBadMinor0m 4mIceBadState0m 4mIceBadLength0m 4mIceBadValue0m 4mIceBadMajor0m 4mIceNoAuth0m 4mIceNoVersion0m 4mIceSetupFailed0m 4mIceAuthRejected0m 4mIceAuthFailed0m 4mIceProtocolDuplicate0m 4mIceMajorOpcodeDuplicate0m 4mIceUnknownProtocol0m For further information, see the 4mInter-Client24m 4mExchange24m 4mPro-0m 4mtocol24m standard. To handle fatal I/O errors, use 4mIceSetIOErrorHandler24m. __ | IceIOErrorHandler IceSetIOErrorHandler(4mhandler24m) IceIOErrorHandler 4mhandler24m; 4mhandler24m The I/O error handler. You should pass NULL to restore the default handler. |__ 4mIceSetIOErrorHandler24m returns the previous IO error handler. An ICE I/O error handler has the type of 4mIceIOErrorHandler24m. __ | typedef void (*IceIOErrorHandler)(); void IOErrorHandler(4mice_conn24m) IceConn 4mice_conn24m; 4mice_conn24m The ICE connection object. |__ There are two ways of handling IO errors in ICElib: - 45 - 1mInter-Client Exchange Library X11, Release 6.40m · In the first, the IO error handler does whatever is necessary to respond to the IO error and then returns, but it does not call 4mIceCloseConnection24m. The ICE con- nection is given a ``bad IO'' status, and all future reads and writes to the connection are ignored. The next time 4mIceProcessMessages24m is called it will return a status of 4mIceProcessMessagesIOError24m. At that time, the application should call 4mIceCloseConnection24m. · In the second, the IO error handler does call 4mIce-0m 4mCloseConnection24m, and then uses the 4mlongjmp24m call to get back to the application's main event loop. The 4msetjmp0m and 4mlongjmp24m calls may not work properly on all plat- forms, and special care must be taken to avoid memory leaks. Therefore, this second model is less desirable. Before the application I/O error handler is invoked, proto- col libraries that were interested in being notified of I/O errors will have their 4mIceIOErrorProc24m handlers invoked. This handler is set up in the protocol registration func- tions (see 4mIceRegisterForProtocolSetup24m and 4mIceRegisterFor-0m 4mProtocolReply24m) and could be used to clean up state specific to the protocol. __ | typedef void (*IceIOErrorProc)(); void IOErrorProc(4mice_conn24m) IceConn 4mice_conn24m; 4mice_conn24m The ICE connection object. |__ Note that every 4mIceIOErrorProc24m callback must return. This is required because each active protocol must be notified of the broken connection, and the application IO error handler must be invoked afterwards. 1m14. Multi-Threading Support0m To declare that multiple threads in an application will be using the ICE library, use 4mIceInitThreads24m. __ | Status IceInitThreads() |__ The 4mIceInitThreads24m function must be the first ICElib func- tion a multi-threaded program calls. It must complete - 46 - 1mInter-Client Exchange Library X11, Release 6.40m before any other ICElib call is made. 4mIceInitThreads0m returns a nonzero status if and only if it was able to ini- tialize the threads package successfully. It is safe to call 4mIceInitThreads24m more than once, although the threads package will only be initialized once. Protocol libraries layered on top of ICElib will have to lock critical sections of code that access an ICE connection (for example, when generating messages). Two calls, which are generally implemented as macros, are provided: __ | IceLockConn(4mice_conn24m) IceConn 4mice_conn24m; IceUnlockConn(4mice_conn24m) IceConn 4mice_conn24m; 4mice_conn24m The ICE connection. |__ To keep an ICE connection locked across several ICElib calls, applications use 4mIceAppLockConn24m and 4mIceAppUnlockConn24m. __ | void IceAppLockConn(4mice_conn24m) IceConn 4mice_conn24m; 4mice_conn24m The ICE connection to lock. |__ The 4mIceAppLockConn24m function completely locks out other threads using the connection until 4mIceAppUnlockConn24m is called. Other threads attempting to use ICElib calls on the connection will block. If the program has not previously called 4mIceInitThreads24m, 4mIceAppLockConn24m has no effect. __ | void IceAppUnlockConn(4mice_conn24m) IceConn 4mice_conn24m; 4mice_conn24m The ICE connection to unlock. |__ The 4mIceAppUnlockConn24m function allows other threads to com- plete ICElib calls on the connection that were blocked by a previous call to 4mIceAppLockConn24m from this thread. If the program has not previously called 4mIceInitThreads24m, 4mIceAppUn-0m 4mlockConn24m has no effect. - 47 - 1mInter-Client Exchange Library X11, Release 6.40m 1m15. Miscellaneous Functions0m To allocate scratch space (for example, when generating mes- sages with variable data), use 4mIceAllocScratch24m. Each ICE connection has one scratch space associated with it. The scratch space starts off as empty and grows as needed. The contents of the scratch space is not guaranteed to be pre- served after any ICElib function is called. __ | char *IceAllocScratch(4mice_conn24m, 4msize24m) IceConn 4mice_conn24m; unsigned long 4msize24m; 4mice_conn24m A valid ICE connection object. 4msize24m The number of bytes required. |__ Note that the memory returned by 4mIceAllocScratch24m should not be freed by the caller. The ICE library will free the mem- ory when the ICE connection is closed. 1m16. Acknowledgements0m Thanks to Bob Scheifler for his thoughtful input on the design of the ICE library. Thanks also to Jordan Brown, Larry Cable, Donna Converse, Clive Feather, Stephen Gildea, Vania Joloboff, Kaleb Keithley, Stuart Marks, Hiro Miyamoto, Ralph Swick, Jim VanGilder, and Mike Wexler. - 48 - 1mInter-Client Exchange Library X11, Release 6.40m 1mAppendix A0m 1mAuthentication Utility Functions0m As discussed in this document, the means by which authenti- cation data is obtained by the ICE library (for 4mConnection-0m 4mSetup24m messages or 4mProtocolSetup24m messages) is implementation- dependent.- This appendix describes some utility functions that manipu- late an ICE authority file. The authority file can be used to pass authentication data between clients. The basic operations on the .ICEauthority file are: · Get file name · Lock · Unlock · Read entry · Write entry · Search for entry These are fairly low-level operations, and it is expected that a program, like "iceauth", would exist to add, remove, and display entries in the file. In order to use these utility functions, the <4mX11/ICE/ICEu-0m 4mtil.h24m> header file must be included. An entry in the .ICEauthority file is defined by the follow- ing data structure: __ | typedef struct { char *protocol_name; unsigned short protocol_data_length; char *protocol_data; char *network_id; char *auth_name; unsigned short auth_data_length; char *auth_data; } IceAuthFileEntry; ----------- - The X Consortium's ICElib implementation assumes the presence of an ICE authority file. - 49 - 1mInter-Client Exchange Library X11, Release 6.40m |__ The protocol_name member is either ``ICE'' for connection setup authentication or the subprotocol name, such as ``XSMP''. For each entry, protocol specific data can be specified in the protocol_data member. This can be used to search for old entries that need to be removed from the file. The network_id member is the network ID of the client accepting authentication (for example, the network ID of a session manager). A network ID has the following form: tcp/: or decnet/:: or local/: The auth_name member is the name of the authentication method. The auth_data member is the actual authentication data, and the auth_data_length member is the number of bytes in the data. To obtain the default authorization file name, use 4mIceAuth-0m 4mFileName24m. __ | char *IceAuthFileName() |__ If the ICEAUTHORITY environment variable if set, this value is returned. Otherwise, the default authorization file name is $HOME/.ICEauthority. This name is statically allocated and should not be freed. To synchronously update the authorization file, the file must be locked with a call to 4mIceLockAuthFile24m. This func- tion takes advantage of the fact that the 4mlink24m system call will fail if the name of the new link already exists. __ | int IceLockAuthFile(4mfile_name24m, 4mretries24m, 4mtimeout24m, 4mdead24m) char *4mfile_name24m; int 4mretries24m; int 4mtimeout24m; long 4mdead24m; 4mfile_name24m The authorization file to lock. 4mretries24m The number of retries. - 50 - 1mInter-Client Exchange Library X11, Release 6.40m 4mtimeout24m The number of seconds before each retry. 4mdead24m If a lock already exists that is the specified dead seconds old, it is broken. A value of zero is used to unconditionally break an old lock. |__ One of three values is returned: · 4mIceAuthLockSuccess24m - the lock succeeded. · 4mIceAuthLockError24m - a system error occurred, and 4merrno0m may prove useful. · 4mIceAuthLockTimeout24m - the specified number of retries failed. To unlock an authorization file, use 4mIceUnlockAuthFile24m. __ | void IceUnlockAuthFile(4mfile_name24m) char *4mfile_name24m; 4mfile_name24m The authorization file to unlock. |__ To read the next entry in an authorization file, use 4mIceReadAuthFileEntry24m. __ | IceAuthFileEntry *IceReadAuthFileEntry(4mauth_file24m) FILE *4mauth_file24m; 4mauth_file24m The authorization file. |__ Note that it is the responsibility of the application to open the file for reading before calling this function. If an error is encountered, or there are no more entries to read, NULL is returned. Entries should be free with a call to 4mIceFreeAuthFileEntry24m. To write an entry in an authorization file, use 4mIceWriteAu-0m 4mthFileEntry24m. __ | - 51 - 1mInter-Client Exchange Library X11, Release 6.40m Status IceWriteAuthFileEntry(4mauth_file24m, 4mentry24m) FILE *4mauth_file24m; IceAuthFileEntry *4mentry24m; 4mauth_file24m The authorization file. 4mentry24m The entry to write. |__ Note that it is the responsibility of the application to open the file for writing before calling this function. The function returns a nonzero status if the operation was suc- cessful. To search the default authorization file for an entry that matches a given protocol_name/network_id/auth_name tuple, use 4mIceGetAuthFileEntry24m. __ | IceAuthFileEntry *IceGetAuthFileEntry(4mprotocol_name24m, 4mnetwork_id24m, 4mauth_name24m) char *4mprotocol_name24m; char *4mnetwork_id24m; char *4mauth_name24m; 4mprotocol_name0m The name of the protocol to search on. 4mnetwork_id0m The network ID to search on. 4mauth_name24m The authentication method to search on. |__ If 4mIceGetAuthFileEntry24m fails to find such an entry, NULL is returned. To free an entry returned by 4mIceReadAuthFileEntry24m or 4mIceGe-0m 4mtAuthFileEntry24m, use 4mIceFreeAuthFileEntry24m. __ | void IceFreeAuthFileEntry(4mentry24m) IceAuthFileEntry *4mentry24m; 4mentry24m The entry to free. |__ - 52 - 1mInter-Client Exchange Library X11, Release 6.40m 1mAppendix B0m 1mMIT-MAGIC-COOKIE-1 Authentication0m The X Consortium's ICElib implementation supports a simple MIT-MAGIC-COOKIE-1 authentication scheme using the authority file utilities described in Appendix A. In this model, an application, such as a session manager, obtains a magic cookie by calling 4mIceGenerateMagicCookie24m, and then stores it in the user's local .ICEauthority file so that local clients can connect. In order to allow remote clients to connect, some remote execution mechanism should be used to store the magic cookie in the user's .ICEauthor- ity file on a remote machine. In addition to storing the magic cookie in the .ICEauthority file, the application needs to call the 4mIceSetPaAuthData0m function in order to store the magic cookie in memory. When it comes time for the MIT-MAGIC-COOKIE-1 authentication pro- cedure to accept or reject the connection, it will compare the magic cookie presented by the requestor to the magic cookie in memory. __ | char *IceGenerateMagicCookie(4mlength24m) int 4mlength24m; 4mlength24m The desired length of the magic cookie. |__ The magic cookie returned will be null-terminated. If mem- ory can not be allocated for the magic cookie, the function will return NULL. Otherwise, the magic cookie should be freed with a call to 4mfree24m. To store the authentication data in memory, use 4mIceSetPaAu-0m 4mthData24m. Currently, this function is only used for MIT- MAGIC-COOKIE-1 authentication, but it may be used for addi- tional authentication methods in the future. __ | void IceSetPaAuthData(4mnum_entries24m, 4mentries24m) int 4mnum_entries24m; IceAuthDataEntry *4mentries24m; 4mnum_entries0m The number of authentication data entries. - 53 - 1mInter-Client Exchange Library X11, Release 6.40m 4mentries24m The list of authentication data entries. |__ Each entry has associated with it a protocol name (for exam- ple, ``ICE'' for ICE connection setup authentication, ``XSMP'' for session management authentication), a network ID for the ``accepting'' client, an authentication name (for example, MIT-MAGIC-COOKIE-1), and authentication data. The ICE library will merge these entries with previously set entries, based on the (protocol_name, network_id, auth_name) tuple. __ | typedef struct { char *protocol_name; char *network_id; char *auth_name; unsigned short auth_data_length; char *auth_data; } IceAuthDataEntry; |__ - 54 - 1mTable of Contents0m 1. Overview of ICE . . . . . . . . . . . . . . . . . . . 1 2. The ICE Library - C Language Interface to ICE . . . . 1 3. Intended Audience . . . . . . . . . . . . . . . . . . 1 4. Header Files and Library Name . . . . . . . . . . . . 2 5. Note on Prefixes . . . . . . . . . . . . . . . . . . 2 6. Protocol Registration . . . . . . . . . . . . . . . . 2 6.1. Callbacks for Processing Messages . . . . . . . . . 8 6.2. Authentication Methods . . . . . . . . . . . . . . 12 7. ICE Connections . . . . . . . . . . . . . . . . . . . 15 7.1. Opening an ICE Connection . . . . . . . . . . . . . 15 7.2. Listening for ICE Connections . . . . . . . . . . . 17 7.3. Host Based Authentication for ICE Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 7.4. Accepting ICE Connections . . . . . . . . . . . . . 21 7.5. Closing ICE Connections . . . . . . . . . . . . . . 23 7.6. Connection Watch Procedures . . . . . . . . . . . . 24 8. Protocol Setup and Shutdown . . . . . . . . . . . . . 26 9. Processing Messages . . . . . . . . . . . . . . . . . 28 10. Ping . . . . . . . . . . . . . . . . . . . . . . . . 30 11. Using ICElib Informational Functions . . . . . . . . 31 12. ICE Messages . . . . . . . . . . . . . . . . . . . . 33 12.1. Sending ICE Messages . . . . . . . . . . . . . . . 33 12.2. Reading ICE Messages . . . . . . . . . . . . . . . 39 13. Error Handling . . . . . . . . . . . . . . . . . . . 43 14. Multi-Threading Support . . . . . . . . . . . . . . 46 15. Miscellaneous Functions . . . . . . . . . . . . . . 48 16. Acknowledgements . . . . . . . . . . . . . . . . . . 48 Appendix A - Authentication Utility Functions . . . . . 49 Appendix B - MIT-MAGIC-COOKIE-1 Authentication . . . . . 53 iii